Collision
by Linzerj
Summary: When Phineas and Ferb built a trans-dimensional portal, they didn't intend to bring anyone out of it! Donatello finds himself in a strange new world after falling through the portal, caused when his portal and the boys' portal caused a space/time rip...
1. The TransDimensional Problem

__To those of you who are unfamiliar with me: Thank you for coming, and welcome to my story! For those of you who do know me...yeah, I know, I have about a million other projects I should be finishing, blah blah...but I couldn't let this idea slip away!

If you're here, I hope you are familiar with Phineas and Ferb, and at least the TMNT movie Turtles Forever. If not, I suggest you watch the movies of both or at least the first episode of both series before continuing. Thank you.

Now...see, I got this idea when I realized both shows had some kind of dimension-hops in them. Phineas and Ferb Across the Second Dimension has the Alternate-Dimension-inator; and Turtles Forever has the trans-dimensional portal, and the portal stick. I thought it would be interesting to see devices similar to these being used to have the two shows meet...and thus, this was born!

I hope you guys are prepared...for a collision of universes!

Disclaimer: I do not own Phineas and Ferb nor TMNT. TMNT belongs to Kevin Eastman and Peter Laird; Phineas and Ferb belong to Jeff "Swampy" Marsh and Dan Povenmire.

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><p><em><strong>Collision<strong>_

_The Trans-Dimensional Problem_

"There! It's done!" The red-haired boy with a triangular head stepped back, gazing upon his completed work proudly. His green-haired step-brother put a hand on his shoulder, to show that he, too, was proud of their accomplishment.

"Um…Phineas, what exactly does this thing…do?" This question came from the only female present at the moment, the black-haired Mexican-Jewish girl Isabella. Phineas smiled.

"Well, Isabella, it's a trans-dimensional portal!" Phineas explained. "You see…"

As he went on to explain a few of the finer workings of the machine, the largest boy, Buford, glanced at the Indian nerd Baljeet. "Do you have any idea what they're talking about?"

"Yes, now please, be quiet, I would like to listen!"

"So in short, this device allows us to open windows to other places!" Phineas was finishing.

"Wow," Isabella said, obviously impressed. "So…we'll finally be able to see where those giant floating baby heads come from?"

"I sure hope so," Phineas replied, glancing around in spite of himself. "Those things are really creepy sometimes." As if to prove his point, a random, giant, floating baby head floated by; the group stared at it, awestruck.

"So anyway," the red-head went on, shaking his head to dismiss the random occurrence, "let's fire it up! Oh, hey, where's Perry?"

In an underground lair just below their feet, the teal-colored platypus dropped down from a chute, a fedora landing on his head. On the screen was a white-haired man.

"Ah, good morning, Agent P," Major Monogram greeted. "Now…ordinarily, we'd have you go after Dr. Doofenshmirtz, but he's sick today, and has not purchased any weird items. We have a few undercover agents staking out his building, just in case he does try something, but we have far bigger matters at hand right now.

"Your boys have built a trans-dimensional portal, similar to the Alternate-Dimension-inator Doofenshmirtz built a few weeks ago. We don't know if this is just coincidence, or a side effect of the Amnesia-inator, but if they accidentally open up into the second dimension, they are very apt to remember everything, and then…we'd have to relocate you, Agent P."

Perry's face fell. He loved his boys, and that day was one of the best days they'd had together; Phineas and Ferb had found out about his secret identity, but after some bumps in the road they had really bonded that day. And it was all gone, just because OWCA's security precautions wouldn't allow for his family to remember. But even with those memories gone, he would not stand for being relocated.

"Your mission for today," Monogram continued, "is simply to make sure the boys don't remember, and don't open a window into that dimension. Our organization rests in your hands, Agent P."

Perry saluted, and then rushed over to the tube that would take him back up to his boys.

"So, ready…set…oh, there you are, Perry!" The platypus made his chatter as the group all looked over to him. "OK, again…ready…set…"

"Hold it right there!" Candace, Phineas and Ferb's older sister, stormed out of the house, blue eyes narrowed dangerously. "Alright, what have you two built this time?"

"It's a trans-dimensional portal," Phineas explained to his sister."We're going to use it to take a peek at some other dimensions, see what they're like. Alright, enough countdowns now; fire it up, Ferb!"

Ferb gave a thumbs up, and then hit a button. The machine whirred and sputtered, and the group gasped as a window began to form…

_In another dimension…_

"Donny, would you stop fooling around with the portal stick?" The blue-banded, katana-wielding Turtle was glaring at his purple-masked brother. The Turtle in question turned around, raising a skeptical eye-ridge at his older brother.

"Leo, I'm just testing to see what a few other dimensions are like," Donatello explained. Their two brothers, Raphael and Michelangelo, padded over.

"Hey Donny, do you think there are dimensions that _don't_ have Turtles?" Michelangelo asked. This earned him a glare from Leonardo, but the orange-masked Turtle continued, "I mean, we exist in this 'Turtle-verse', but I wonder if there are other dimensions out there, you know?"

"Hmm…" Don's chocolate eyes became thoughtful. "It's possible… let me change a few of the calibrations, and we'll find out."

"Just don't do anything dangerous, Brainiac," Raphael muttered, leaning over his brother's shoulder. "I don't wanna have a horde of…of…of giant floating baby heads take over NYC, for example."

The red-masked Turtle then noticed the looks he was receiving from his brothers. "What?"

Leo rolled his eyes. "Alright, whatever, just…do you know what you're doing, Donny?"

"Yeah, Don, I don't really want any giant floating baby heads in our lair," Mikey added. This earned him a slap on the back of the head from Raph. "Ow! What?"

By this point, Don had pushed the button to activate the trans-dimensional portal stick. There was a whirring sound, and a bright flash filled Don's lab. The Turtles gasped.

"Don…where does it lead to?" Leo asked, his voice just above a whisper.

"I'm…not sure," Don replied, equally quiet. "But…"

The purple-masked Turtle moved to stick his head through the portal. The eyes of his three brothers widened.

"Donny, what the shell are ya doin'?" Raph demanded.

"Relax," Don replied. "I've got it under contro-aaah!"

"DONNY!"

Donatello had tripped on a loose wire, and was falling through the portal. Mikey grabbed for his brother, but Leo and Raph pulled him back as Don disappeared into the portal. Once he was through, the stick whirred, and the portal faded as the machine shut off. Mikey's blue eyes were wide.

"Donny? Donny! DONNY!"


	2. Sorry, Wrong Dimension

...I like cliffhangers. Expect lots of them! xD

I hope you guys are entertained by this story. I, for one, am really liking it. I don't plan on it being too long, but it won't end for a few more chapters, either. Still, enjoy!

Disclaimer: I do not own Phineas and Ferb nor TMNT. TMNT belongs to Kevin Eastman and Peter Laird; Phineas and Ferb belong to Jeff "Swampy" Marsh and Dan Povenmire.

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><p><em><strong>Collision<strong>_

_Sorry, Wrong Dimension_

Donatello groaned as he blinked open his eyes. "Ooh..." he muttered, putting a three-fingered hand to his head. "Wha...what happened...?"

Then his chocolate eyes snapped open. The trans-dimensional portal stick - he had fallen through the window! He could be anywhere in the multi-verse! And if he was anywhere... he glared at the grass in front of him. He had no idea if he was in a hostile or friendly situation...

"Do you think he's OK?" The quiet, timid voice snapped him to attention. In one fluid motion, Don pushed himself to his feet, grabbing his bo and twirling it as he spun around and assumed a battle stance, glaring at the source of the voice.

He was shocked at what he found, and almost lost his stance. Standing before him were four boys, two girls, and...was that a platypus? All were looking at him with mixtures of fear, confusion, and curiosity. But even though they were kids, he wasn't about to just...trust them with his life.

"Who are you?" he demanded, pointing his bo at them. "Why did you bring me here?"

"Easy, easy." The kid who had spoken earlier, the boy with red hair, blue eyes, and a triangular-shaped head, put his arms up in the universal symbol of peace. "We...we don't mean you any harm, and we didn't mean to bring you here. We...my name's Phineas. This is my stepbrother Ferb, my sister, Candace, and our friends Isabella, Baljeet, and Buford." Donatello looked them over without dropping his defensive stance: kid with green hair, teenage girl, black-haired girl, Indian kid, and boy with a skull on his shirt. His eyes then locked with the platypus. Behind the vacant-looking face, he could see the brown eyes were examining him, too.

"Oh, that's Perry." The voice nearly caught Don off guard again, and he turned back to the kid with red hair. He had walked a few steps closer, and had now backed up. The fear in his expression suddenly melted into annoyance.

"Look, we're trying to help you, here!" he all but shouted. "We didn't mean to bring you here, but if you won't accept our help-!"

Don sighed, lowering his bo staff. "I...sorry," he mumbled. "I'm just...used to people either freaking out on sight, or else trying to kill or dissect me."

Phineas's disgusted expression almost made Donatello want to laugh. "Ugh, gross. Well, we won't dissect you, I promise."

The oldest, the red-headed girl, Candace, had shaken off the shock. "OK, so what exactly _are_ you?" she demanded.

Don twirled his bo staff before putting it back in his belt; he then did a formal Japanese bow. "My name is Donatello," he said, straightening up. "I...I'm a Turtle. A teenage mutant ninja Turtle."

The expressions of shock and curiosity were back. Donatello had to refrain from laughing. It was the black-haired girl, Isabella, who spoke next.

"Well, Donatello," she said, stepping forward. "Welcome to Danville. Where are you from, anyway?"

Don resisted the urge to snort. "Another dimension, obviously. But if you want to be specific...New York City."

Phineas's blue eyes lit up. "Really? That's so cool! I've always wanted to go to New York City - right, Ferb?" The green-haired boy nodded in agreement. Donatello smiled sheepishly, and then glanced at the machine.

"So...that's your trans-dimensional portal, then?"

"Yeah," Buford answered before anyone else could open his or her mouth. "The guys just finished building it, and were testing it out when you showed up."

"Fascinating technology!" Don had regressed into techno-geek mode, and now the gang had to supress laughs as the Turtle critically examined their work. "And...you guys aren't even teens, are you? Except for you, Candace - obviously," he added at the annoyed glare.

"I'm sixteen, for you information," Candace all but spat. "And these guys are all ten."

Chocolate eyes widened behind the purple mask. "Only _ten_? And yet...you guys just broke half the laws of physics here!"

"Oh, we do that kind of stuff every day," Phineas said nonchalantly. Don's eyes were ready to fall out of his skull.

"Holy shell! That's incredible!"

Phineas laughed. "Yeah, you should have seen some of our other stuff! For example, we've built a rollercoaster through town, built fifty-foot tree-house robots, went into space on multiple occasions, travelled across the world, built a beach in the backyard, became one-hit wonders, made winter in the middle of summer, put on a circus, made a monster truck arena..." Don's head was spinning. "...had a chariot race through downtown, carved our faces into a comet, accidentally switched Perry's and Candace's brains-"

"Worst day ever!" Candace added in.

"...Built a haunted house, made an animation studio, made a portal to Mars, made a restaurant, made an interactive video game, found the Lake Nose monster-"

"Isn't it Loch Ness monster?" Don asked, confused by this one project. Phineas shrugged.

"Maybe in your dimension, but here it's Lake Nose. Anyway...we made a shrinking machine, X-ray vision goggles, became detectives, found the lost city of Atlantis, made an anti-gravity fun lancher, became superheroes, and so. Much. MORE! Oh, and we travelled through time twice."

At this, Don groaned. "You know, I've had enough time travel to last me a lifetime, thanks. Try being stuck a hundred years in the future with the future grandkid of your two best friends for over a year!"

Phineas shrugged. "I wouldn't know. When we went through time, the first was back to the age of the dinosaurs, and then we went into the future to see if we had fixed it when a future Candace came and accidentally messed it up."

Donatello was at a loss for words. "O...kay?" The Turtle shook his head. "But, look, I've gotta get back - my brothers are probably worried sick about me by now. Could you...help me out?"

Phineas grinned. "Sure, no problem! We'll just fire this up..."

Ferb hit the button, and the machine whirred...but the window was not into Don's world. He frowned.

"Huh, whaddya know, Raph was right - there _is_ a universe filled with giant floating baby heads."

"_That's_ where those things keep coming from!"

"It's not my dimension, though," Don muttered as Phineas deactivated the portal.

"Well, do you have any coordinates we could use?"

Don shook his head. "No..." Then his eyes lit up. "Actually...I think that the crossing fluxes of your portal and mine caused the space/time continuum to rip between our dimensions. Unless we can find the coordinates," Don's voice became strained, "or unless I can contact my brothers somehow and tell them to fire up the portal, then I'm stuck here - for good!"


	3. Talking It Out

So...there's a lot of talking in this one. I don't know why. There's a lot of Don just babbling on to Perry, too. This will actually be key for several reasons...and you'll see why.

Disclaimer: I do not own Phineas and Ferb nor TMNT. TMNT belongs to Kevin Eastman and Peter Laird; Phineas and Ferb belong to Jeff "Swampy" Marsh and Dan Povenmire.

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><p><em><strong>Collision<strong>_

_Talking It Out_

Raphael angrily slammed a fist down onto the computer console. "Ugh! We should've - I should've - we shouldn't've let 'im play wit dat stupid thing!" He pointed at the object in question, the trans-dimensional portal stick laying innocently on the table. Amber eyes blazed with fury as a sai was launched mercilessly at the nearby punching bag, effectively piercing it.

"Raph, yelling about it isn't going to help Don," Leonardo murmured, putting a hand on his brother's shoulder. His dark eyes, however, betrayed his worry. "We'll get him back, I know we will."

"But...but Donny's the only one who knew how to work this thing," Mikey said, tears still watery in his blue eyes. His voice shook, and he was still sniffling. "I mean, I know we just push the button to activate it, b-but I dunno how to switch the settings..."

"Michelangelo, it will be alright." The furry hand of Master Splinter rested comfortingly on Mikey's shoulder. "We will find your brother...somehow."

Suddenly, Leo's eyes widened. "Wait a minute...did Donny ever get around to upgrading the shell-cells?" Raph raised an eye-ridge.

"Leo, why does it matter if Don upgraded the shell-cells?" Raph asked.

"I...I think he did," Mikey said, pondering it. "I don't really remember...maybe he did it when we were all sleeping in that one day."

Leo was pacing know, thoughts running wild. "If Donny upgraded the cells," he contemplated, "then he would've installed trans-dimensional calling! Don was telling me about how he wanted to make it so that if we ever have some issues with the portal stick, we could reach each other without worrying about trans-dimensional boundaries!"

Raph's amber eyes went wide. "Do...do ya think he installed it?"

Leo's dark eyes narrowed. "I don't know," he muttered, retrieving his own shell-cell. "But it can't hurt to try."

* * *

><p>"Nope. Nu-uh. Ew, how could you think I live there?"<p>

"Well, you do smell like a sewer."

"Gee, thanks for the compliment."

"Hey, guys, come on now, we're trying to work," Phineas said, glaring at Buford and Don, who were glaring daggers at each other. Don sighed, glancing away from the young bully.

"I know, and I appreciate your help, Phineas," Don murmured. "I really do. But...just flitting through dimensions like that...well, it could take eons before we find the right one. There are hundreds, thousands, _millions_ of dimensions to search through!"

Phineas sighed, signaling to Ferb to shut down the machine. "I know, Don, but at least we're trying. Without the exact coordinates...we're kinda stumped." The young boy glanced up at the sun, and as if on cue, his stomach rumbled. "Wanna take a break? I'm getting kinda hungry."

"Yeah, me too."

"I, too, am hungry."

"Buford want food!"

Candace sighed, turning and padding toward the house. "I'll make sandwiches or something," she grumbled. Phineas smiled, but turned to Donatello before following the others inside.

"Do you wanna come? Candace can make a mean grilled cheese."

Don shook his head. "No, thanks - I'll stay out here with Perry. Thanks, though."

Phineas shrugged, and then turned to race after his friends. Don sighed as he watched the boy depart; once the door slid shut, he turned to Perry. Chocolate eyes met bright brown eyes, and Don mentally frowned; there was something eerie about the way the platypus's eyes were reading him.

"I have a feeling you're smarter than they give you credit for," the Turtle muttered, sinking into the soft grass next to the platypus. "And believe me, I wouldn't be shocked at all if you could walk and talk."

The look Perry gave Don was almost surreal; it was as though the platypus was thinking, _I am a lot smarter than they know...but I'm not about to trust you with that kind of information_. At the look, Don smirked and patted his head.

"Well, you're more than mindless, I can see that." The Turtle sighed, flipping over so that he lay on his shell, looking up at the sky. "You know, Perry, this place is nice and all...but I really miss home."

Perry chattered, as though he meant to say, _Yeah, I know the feeling._ Don glanced over at the platypus, and found himself struggling to maintain a calm face. The brown eyes that bore into his own...they were definitely not the eyes of a mindless animal. Perry was something unique, even in the world of the teenaged mutant ninja Turtle Donatello.

Suddenly, there was a beeping - and Don almost forgot to answer, because he was mesmerised by the teal platypus. The way he had scuttled back...for a moment, just a moment, he had actually _walked on two feet_. Don shook his head. He could deal with that later, he decided, as the shell-cell continued to beep.

The purple banded Turtle flipped open the device, and thus had answered the call; but he hesitated as he put it to his ear, afraid of what he might hear. "Uh...hello?"

"_DONNY!"_ The group cheer was loud and staticy - and at that moment, Don remembered putting in that feature that would allow him to call his brothers from different dimensions. Oh well, he could kick himself over forgetting that later.

"Mikey, Raphy, Leo! I can't believe I'm hearing your voices!"

"_Well, just barely, huh - there's all this static."_

"Ah, a side effect of trans-dimensional calling," Don said, waving it off. Then his eyes widened - there was a crash in the background. He winced as Leo yelled, "_Mikey, knock it off! I'm trying to talk to Donny!" _

"What's that chuckle-head up to now?" Don asked, amusement in his voice.

"_Well...we're trying to figure out how to charge the portal stick. It...kinda ran out of batteries."_

"It's simple - all you have to do is pull out the extension cord and plug it in." Leo muffled the phone this time, but Don could hear some scrabbling and a few things falling. Then Raph got on the phone.

"_Alright, genius, we got the thingy charging,"_ the hot-headed Turtle said. "_But man, I can't believe I'm hearing you! How are ya? What dimension are you stuck in?"_

"Uh...a pretty interesting one," Don said, glancing first at Perry and then at the house. "Listen, Raph, there's these kids - they're only ten, but they built their own trans-dimensional portal!"

There was a pause; then, Raph's gruff laughter. "_Yeesh, Donny, you must be in your element over there."_

"Yeah, you could say that. Oh, Raph - I have to tell you something. I have a theory on how to get home!"

"_What? Spill!"_

"OK, first you'll just need to - gah!" Suddenly, there was a screech like a microphone being tapped, and then static. "Raph? Raph!" A click - the line was dead.

Don growled, slamming a fist in the grass. "No!" he complained to Perry. "No, I was _so close!_"

He let his head fall back into the grass, and glared up at the sky. "As Raph would say...great. Just great. The old Turtle luck's running true to form." He sighed, rolling over so his face was now buried in the soft green grass. "Ugh! Why does the universe hate me?"

There was a comforting hand laid tentatively on his shoulder; at first, he thought it might be Phineas or Ferb or one of the others, but none of them had furry hands. Don risked a look...and gasped.

Perry was standing on his hind legs, a fedora on his head, looking down at Don with genuine, utter sympathy.


	4. Nerds of a Feather

We're progressing on with the story. Look, Doofenshmirtz appears - and there's some more Don geeking out moments, too! And look - Donny has an idea!

Disclaimer: I do not own Phineas and Ferb nor TMNT. TMNT belongs to Kevin Eastman and Peter Laird; Phineas and Ferb belong to Jeff "Swampy" Marsh and Dan Povenmire.

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><p><em><strong>Collision<strong>_

_Nerds of a Feather_

Don shook his head, blinking in shock at Perry. The platypus offered a sheepish grin as he removed his paw from the Turtle's shoulder and tipped his fedora.

"You...you're...wow," Don breathed, getting into a sitting position. "I just...I can't believe...how's this possible?"

Perry shrugged, and Don almost wanted to laugh. "Well, sitting around talking isn't going to get us very far, huh?"

Perry shook his head; and then, there was a beeping. At first, Don thought it was his shell-cell; but then, Perry looked down to his wrist, where Don saw a watch that was beeping at him.

"_Agent P," _a gruff male voice said, "_some of our agents down at Doofenshmirtz's have noticed him using some type of -inator...but we are unsure of what it does. We need you to get down there and see what this is all about."_

Perry saluted, and as the watch turned off, turned to look at Don, who was staring at him in partial shock. Finally, Don sputtered out, "Doofenshmirtz? What the heck kind of a name is Doofenshmirtz?"

Again, Perry shrugged, and then began to pad away. He stopped, though, turning to look back at Don, who had by this time risen to his feet. A pen and paper were whipped out of the fedora, and the platypus scribbled something down before ripping out the sheet and handing it to Don. Then, with a salute, the platypus was off.

Don stared after the teal shape for a moment, before looking down at the sheet and reading it aloud to himself. "Don, don't tell anyone about me...blah blah blah...Doofenshmirtz is an evil scientist, and I have to stop his schemes, blah blah...I have a feeling he might have been messing with the frequencies...what?"

The Turtle looked up from the note, towards the door Perry had exited from, but the platypus was long gone. With a shrug, Don folded the note and put it in his pocket before turning toward the house. Hey, talking to a platypus and wondering when you're going to go home sure does work up an appetite.

_Doofenshmirtz Evil Incorperated!_

The teal shape of a platypus bursting through the door had the brown-haired scientist whipping around. "Perry the Platypus? What-oof!"

Already, Perry had kicked Doofenshmirtz, and was rushing over to examine his latest -inator. But Doof was one step ahead of the platypus. Pressing a button, arms sprang out of the floor and grabbed onto Perry's legs and arms, stopping him just short of the machine.

"Wow, Perry the platypus, you really want to know what's going on with this machine, huh?" Doof inquired. "Well, BEHOLD! THE FREQUENCY SCRAMBLER-INATOR! With this device, I am able to scramble frequencies of radio stations, telephones, any device! And once people become tired of having to do things the old fashioned way, they shall come to ME! And all they'd have to do for me to unscramble their calling frequencies would be to accept me as the leader of the TRI-STATE AREA! AA-HAHAHAHA!"

Perry just rolled his eyes. Well, that explained why Donatello's call had been staticy when he was trying to contact his brothers. Still...as always, it was his job to stop Doofenshmirtz's schemes from succeeding. And the doctor hadn't learned from the last time he'd trapped the secret agent with mechanical arms...

A loose screw lying by Perry's tail was all he needed. He lined up the shot with the button on the wall that said 'Arms Release'. It was an easy shot, and Perry fired. The screw sang true, and hit the button, releasing Perry.

"Perry the Platypus! How did you escape? Oh, no time for that!" Doof was now rushing over to his machine. "Gotta - get it - powered up - before - OOF!"

Perry had kicked the evil scientist square in the jaw, forcing him onto a button that read 'self-destruct'. Doof sighed. "Oh, great."

He made no real effort to get away; Doofenshmirtz was used to his inventions blowing up in his face by now. Perry, however, was already jumping out the window and deploying his parachute. Through the bang of the explosion, he could hear Doof yell, "Curse you, Perry the Platypus!"

Aah, all in a day's work.

* * *

><p>"Oh...wow! This thing is awesome!" Don was watching the baseball swivel in the air with wide eyes. Phineas laughed as he controlled the baseball launcher.<p>

"Yeah, it is pretty cool, huh? These guys are the one invention that's never disappeared."

At this, Don's eyes went wide. "So...so you're saying that...that the portal might disappear before I get to go home?"

Phineas now looked guilty. "Um...I dunno. I mean, some of our inventions disappear, but not all of them. For example - see that fort over there? Underneath it is an even bigger fort. That one never went away. And we gave a few away, too, like our restaurant and monster truck arena and the Football X-7 stadium."

"Football X-7?"

"It's better if you don't ask."

"Oh, but it sounds like fun!"

"Nerd alert," Buford muttered to Isabella; this earned him a smack on the head, courtesy of Don's bo staff. "Ow!" The bully turned to the Turtle, glaring, but his glare faded instantly upon seeing the half annoyed, half amused look that crossed Donatello's face.

"I can hear you, you know," Don pointed out. Buford giggled nervously, and Don rolled his eyes, turning back to Phineas and putting his bo away - but not before muttering (under his breath), "Shell for brains."

"Hey, Don, wanna give us a hand here?" Phineas asked as Ferb popped his head out from under the machine. The red-haired boy had put the baseball launcher aside, and was once again working on the trans-dimensional portal. Don cocked his head, and answering the unasked question, Phineas continued, "We're trying to see if the coordinates of your dimension were recorded before the system went on the fritz."

"Oh, sure! Now, let's see here..." Instructions were shouted, findings voiced, and Buford and Isabella stood off to the side as Baljeet joined the nerd-fest, helping with equations and whatnot.

"I really have no idea what they're doing," Isabella whispered to Buford. "But Phineas looks _so_ cute when he's working..."

"Why not just smash the thing?"

"Buford, anyone else would know better than that."

Several minutes later, Don sighed as they once again failed to find his dimension. "It's hopeless," he muttered. "I'm going to be stuck here for- oh, there you are, Perry."

The teal platypus chattered as Phineas broke into laughter. "Dude, you just nailed one of our catchphrases on the first try, and after knowing us for barely three hours!"

Don grinned. "It's a gift." Turning back to the machine, he gave it a kick. "But like I said before...it's hopeless. I'm going to be stuck here forever!"

"Don't say that, Don," Phineas said, eyes big and pleading. "We'll find a way to get you back to your dimension, I promise!"

"Don't make empty promises, Phin," Don muttered, avoiding everyone else's eyes. "I have to contact my brothers _somehow..._!" The Turtle's eyes widened. "Wait...wait, that's it! I found it!" Don proceeded to sit, cross-legged, and assumed a meditative stance.

"Um, I don't mean to dampen the mood," Phineas began, "but...?"

"How will meditating accomplish anything?" Baljeet finished.

"My brothers and I were trained in ninjitsu," Don explained, not opening his eyes. "We were all taught how to meditate, how to reach the astral plane and contact each other's spirits! I've done it before with my father, Master Splinter, but...never from another dimension." Taking a deep breath, he contined, "If you'll just give me some peace and quiet...we'll see if my idea works."


	5. Contact and Plans

So...let's see if Don's idea works! We're coming down to the wire - and I might actually finish this...even though it seems no one's reading it! xD *shot*

Disclaimer: I do not own Phineas and Ferb nor TMNT. TMNT belongs to Kevin Eastman and Peter Laird; Phineas and Ferb belong to Jeff "Swampy" Marsh and Dan Povenmire.

* * *

><p><em><strong>Collision<strong>_

Contact and Plans

_Don's eyes snapped open, but not to see Phineas, Ferb, and all the other Danville kids. No - he was simply floating in a vast void, full of only white light and mist._

_"Hello?" His voice echoed throughout the space - and he realized that he really was on the astral plane. It would be easiest to contact either Master Splinter or Leo, since they were most in tune with the astral plane out of all of the Hamato family, and so he started to walk/float around, trying to see if he, Donatello, could find their auras._

_"HELLO? Sensei? Leo? Can you guys hear me?"_

_Suddenly, there was a shimmer in front of him, and the purple-banded Turtle stopped, blinking. When at last his vision focused, he saw before him..._

_"LEO!" He knew it was only their spirits, that this _technically _wasn't real, but he couldn't resist the urge to tackle-hug his older brother._

_"Donny!" Leonardo's cry was equally joyful - though not as loud - and the blue-banded Turtle accepted the embrace with warm, open arms. "Oh, Don, we miss you...what's going on, anyway?" he said, stepping out of the hug but keeping his hands on Donatello's shoulders._

_"It's...it's an incredible phenomenon, Leo!" Don said, his geek side taking over even here. "But, basically, our portal and another portal were activated at the same time, and together created a rip in the space-time continuum that landed me in the dimension I'm currently in. I'm in this town called Danville, and - oh, Phin, you should see these kids! They're, like, ten years old, but they basically broke half the laws of physics with their portal!"_

_Leo's dark eyes widened with partial shock. "Wow, Don...well, it seems you're in good hands, at least."_

_Don grinned sheepishly. "Yeah...but I wanna go home _so bad_, bro. I miss you and Mikey and Raphy..."_

_"I know, bro," Leo murmured, hugging him again. "We miss you too. But," he added, pulling back out of the hug, "you_ do_ have a plan to get home, right?"_

_"As a matter of fact," Don replied, grinning, "I do, and that's why I tried to contact you again. Something was messing up the shell-cells...maybe we can try them again if we need to, but listen, exactly fifteen minutes after we leave here, I _need _you to fire up the portal stick!"_

_"What? Wait, why?"_

_"Because," Don explained, "I'm going to have these kids, Phineas and Ferb, fire up _their _portal at the exact same time, and hopefully re-create what happened before!"_

_"I dunno, Don," Leo mused, frowning. "I...what if it doesn't work?"_

_"If it doesn't," Don said, "then I'll try the shell-cells again. I'll call you guys, and you guys will have to get the coordinates of our dimension from the portal stick. That way, I can plug them in, and that way I'll be able to get home. ...But this was is much easier than trying to find our coordinates - trust me!"_

_Leo was still frowning, but his eyes softened. "OK, bro," he murmured. "I trust you...and I _really_ hope your plan works!"_

* * *

><p>Don gasped as his eyes snapped open again. The astral plane had slipped away, and he found several pairs of blue eyes - all of varying shades - and one pair of hazel-brown eyes staring at him in concern. He frowned.<p>

"Guys, you're sucking the oxygen right out of my personal bubble here."

"Hey, you're alive!" Candace said, obviously happy. Don rolled his eyes.

"Well, duh," he said, a hint of sarcasm laced in his voice. "I was only meditating."

"Oh, so that's what you were doing?" Phineas asked again. "Why were you meditating."

"It's one of the first things my brothers and I learned to do when our sensei was teaching us ninjitsu," Don explained, getting to his feet. At more confused stares, he sighed. "I'm a ninja. Meditating is essential for ninjas in order to control their emotions, sense other people-"

"But how does that help us at all?" Buford demanded, cutting in. Don smirked.

"And when meditating, we can reach what's called the astral plane and contact the spirits of others, so long as they are extremely in tune with their surroundings or if they are meditating as well," Don finished, crossing his arms with a smirk.

"Oh, so it's like a spiritual phone call sort of thing!" Isabella finally deduced.

"Yeah, sure."

"Alright, then," Phineas said to Ferb as the green-haired Brit shrugged. "So, what's the plan, Don?"

"Well, I contacted my oldest brother, Leo," Don explained. "In fifteen minutes - no, make that thirteen, it was fifteen from the moment we exited the astral plane - so in thirteen minutes exactly, we've gotta fire up that portal."

"And then get you home?" Baljeet inquired. Don sighed, nodding.

"At least, that's the plan..."


	6. Departure

This shall be the final chapter. I finished a story, woohoo! Hope you all enjoyed!

Disclaimer: I do not own Phineas and Ferb nor TMNT. TMNT belongs to Kevin Eastman and Peter Laird; Phineas and Ferb belong to Jeff "Swampy" Marsh and Dan Povenmire.

* * *

><p><em><strong>Collision<strong>_

Departure

Donatello sighed as he put finished adjusting the little system. "Not really. Do I have to?"

"You sound like a five-year-old," Ferb commented. It was the first Don had heard him spoke; the green-haired boy had a British accent, which Don would have asked about had he the time to do so.

"Hey, I'm stressed," the Turtle protested. "I just wanna go home~."

Phineas had to keep himself from giggling, while Isabella just burst out into a fit of giggles. Ferb rolled his eyes, and Baljeet snorted.

"Alright, whateva," Buford grumbled. "C'mon, let's get this show on the road!"

"Okay, then, Phineas," Donatello said, checking his watch. "Fire it up in three...two...one...!"

* * *

><p>Leonardo quirked an eyebrow at Raphael and Michelangelo. "Are you guys sure?"<p>

"Positive," Raph grunted as he finished adjusting the portal stick.

"Oh, it'll work, Leo," Mikey said, popping his head out from under the table; Leo wasn't sure how his youngest brother had gotten there or what he was even doing down there. "And _when_ it does, you can NEVER touch another toaster!"

"It wasn't my fault the last five toasters exploded!" Leo protested. "They just...uh...Donny tinkered with them or something!"

"Hey, don't blame the braniac when he's not here, Fearless," Raph said, shaking his head. "And besides, that's not the point. We've gotta get said Brainiac back!"

Leo cracked a grin. "Alright," the oldest Turtle said, checking his watch. "Mikey, fire it up...NOW!"

* * *

><p>Don shielded his eyes from the flash. "Did it do this before?" he asked, shouting over the whirr of the machine.<p>

"YEP!" came Phineas's reply. The noise died down slightly, and Don took a chance and approached the portal.

"Well?" Isabella inquired after a moment. "Did it work?"

"Buford wanna know!" Buford added. Baljeet rolled his eyes.

"Now you sound like a five-year-old."

"Watch it, nerd."

"It's home!" Don exclaimed, pulling back after a second. His chocolate eyes were sparkling. "I'm going home!"

"Hey, don't we get goodbyes first?" Phineas asked, the hint of a laugh in his voice. Don chuckled as Perry chattered, seconding Phineas's request.

The Turtle held out a hand for Phineas first, and the red-head took it with a grin. As Don went from one kid to the next, he said, "Thanks, guys...for everything. I might not be getting home if it wasn't for you." He ended by patting Perry on the head before rising and turning to the portal.

"Hey," Phineas said, making Don hesitate for another second. "It was fun. I'm glad we met, Donatello."

Don shot a grin back over his shoulder, before waving and jumping through the portal without another word.

* * *

><p>The purple-banded Turtle landed with a grunt. He stumbled, but before he could fall dark green hands caught him.<p>

Don looked up into the amber eyes of his hot-headed brother, and broke out into a grin. "Raphie!"

"Donny!"

"Donny, woohoo!"

"Welcome back, Don!"

The braniac suddenly found himself in a crushing group hug, his brothers all talking at once. He laughed. "Hey, guys, I missed you too!"

"Never, NEVER, do something like that again!" Leo said, breaking away. His smile had melted into a stern frown, and Don smiled sheepishly.

"Aww, Leo, you know I'd never do something like that on purpose," he said.

"Could'a fooled me," Raph commented.

"The important thing," Mikey said, hugging Don again, "is that you're back, Don!"

With a chuckle, Don hugged Mikey back. "It's good to be back, Mikey...it's good to be back."


End file.
